Apparatus for casting molten metal in bottom-pouring molds

ABSTRACT

First chamber means define a vertically elongated first chamber and have a bottom formed with a bottom opening communicating with said first chamber. The first chamber means are provided with an overflow inlet communicating with said first chamber on a predetermined intermediate level thereof. Second chamber means define a horizontally elongated second chamber, which is smaller in cross-sectional area than said first chamber and has one end portion communicating with said bottom opening and an opposite end portion formed with an upwardly directed opening adapted to communicate with a bottom-pouring ingot mold. A plug is operable to selectively close and open said bottom opening.

United States Patent Tenner [151 3,705,616 M51 Dec, 12,1972

APPARATUS FOR CASTING MOLTEN METAL IN BOTTOM-POURING MOLDS Oskar Tenner,Rossatz, Austria Inventor:

Assignee: Fa. Gebauer 8: Lehrner, Vienna,

Austria Filed: April 23, 1970 Appl. No.: 31,121

[56] References Cited UNITED STATES PATENTS 11/1969 Goetz et a1...l64/l33 3/1895 Potter ..249/109 X FOREIGN PATENTS OR APPLICATIONS704,825 4/1941 Germany ..164/363 Primary Examiner-Robert D. BaldwinAttorney-Ernest G. Montague 57 ABSTRACT First chamber means define avertically elongated first chamber and have a bottom formed with abottom opening communicating with said first chamber. The first chambermeans are provided with an overflow inlet communicating with said firstchamber on a predetermined intermediate level thereof. Second chambermeans define a horizontally elongated second chamber, which is smallerin cross-sectional area than said first chamber and has one end portioncommunicating with said bottom opening and an opposite end portionformed with an upwardly directed opening adapted to communicate with abottom-pouring ingot mold. A plug is operable to selectively close andopen said bottom opening.

10 Claims, 1 Drawing Figure PATENTEDHEBIZ I912 3.705.616-

JNVENTOR. (244m (W APPARATUS FOR CASTING MOLTEN METAL IN BOTTOM-POURINGMOLDS The present invention relates to an apparatus for casting moltenmetal in ingot molds, in which apparatus molten metal flows from a ladleor melting furnace through two chambers into runners, from which themolten metal rises from bottom to top into the mold cavities of theingot mold.

lt is known to apply pressure to the surface of a molten bath in acrucible or other vessel, so that the molten material is forced througha riser into a casting mold, such as an ingot mold. In the knownlow-pressure process, the required pressure is applied to the surface ofthe molten bath by a gas under low pressure, which gas may consist,e.g., of air or nitrogen or a rare gas.

A development of the low-pressure process is known as the Alumascprocess, in which a small superatmospheric pressure is applied to themolten metal to force the latter through a riser into the mold. When thecasting has solidified, the superatmospheric pressure is removed, sothat the molten metal is torn at the outlet end of the riser.

The known casting processes of that kind for a mechanical charging ofcasting molds have various disadvantages, so that they cannot be used toproduce large numbers of castings per unit of time. In the casting ofbrass in ingot molds or of aluminum alloys and generally of moltenmaterials tending to oxidize, these processes have the disadvantage thatoxide films form on the surface of the molten bath andin the riser, ofthe system and may be entrained to enter the casting mold during eachcasting operation, so that the quality of the casting is adverselyaffected. Whereas the formation of such oxide films can be restricted oravoided by the use of a non-reactive gas, such as nitrogen, or even arare gas, rather than of atmospheric air, it will be understood that theuse of such gas will increase the manufacturing costs, so that theeconomy of the casting process will be adversely affected. Also in theknown processes the cycle times are too long in view of the largenumbers of castings which are desired per hour because a graduallyincreasing pressure must be applied to the surface of the molten bath,the molten metal must then be forced into the mold through the riser(charging step) and, when the charging step has been completed, thepressure applied to the surface of the molten bath must be sufficientlyreduced, so that the molten metal can separate from the mold inlet andfall in the riser to the level of the surface of the molten bath.

The riser leading to the mold extends into the soaking vessel orcrucible and the level of the surface of the molten bath in said vesselor crucible necessarily changes widely during operation because thesurface is lowered to a predetermined extent after each charging of themold. As a result, the level of the surface of the molten bath variescontinually between an upper limit, which is attained when the soakingvessel has been refilled with molten metal from the melting furnace, anda lower limit, which is reached when the level of the bath surface hasbeen lowered toward the end of the casting operations. This will resultin different cycle times, which will be a minimum when the vessel hasbeen refilled with molten metal to the upper limit of the surface leveland which will be a maximum when refilling is required. It will beunderstood that the flow of molten metal from the transport vessel intothe soaking crucible during the refilling of the latter with moltenmeta] tending to oxidize will result in an entrainment of air,particularly when atmospheric air is used as a fluid for applyingpressure to the molten material. This results again in a formation ofoxide skins and, to some extent, of oxide foam.

It is also known to cast in top-pouring molds. In this case, the moltenmaterial flowing from the ladle is cast directly into the mold whichstands on a plate and the nozzle of the ladle is closed by means of aplug.

This process has the additional disadvantage that the fall of the moltenmaterial through the atmosphere results in the formation of an oxidelayer in an amount which is even larger than in the above-mentionedlowpressure process because a large amount of air is entrained. Anotherdisadvantage resides in that the velocity at which the molten metalenters the mold cannot be controlled.

It is one object of the present invention to provide an apparatus forcasting metal in removable molds, wherein these disadvantages are.avoided by the apparatus provided according to the present invention forcasting molten metal.

It is another object of the present invention to provide an apparatusfor casting metal in molds, wherein the essential feature of the presentinvention resides in that a ladle or melting furnace is connected by aconnecting pipe or an overflow to a vertically elongated housingdefining a chamber for receiving the molten metal, a bath surface ismaintained on a constant level in the chamber, the latter having abottom opening, which can be closed by a conventional plug andcommunicates with one end of a horizontally elongated, second chamber,which is smaller in diameter than the first-mentioned chamber and formsa duct having at its opposite end an upwardly directedl opening, and acasting mold is adapted to be fitted onto the latter opening, so thatsaid mold is disposed below the level of the bath surface.

In an embodiment of the present invention, the plug may be connected inknown manner to a guided stopper rod, which extends freely into themolten'metal from above and is adapted to be controlled by hand or byelectric or electronic means.

The two chambers may be electrically heated by conventional means whichare not part of the present invention. The cross-sectional areas of thetwo chambers and the ratio of said areas will depend on the expectedrate of molten metal.

The arrangement according to the present invention will result in theadvantage that the level of the bath surface and with it the staticpressure in the chamber can be held constant. Besides, the oxidation ismuch reduced because the contact area between air and molten metal isminimized. The molten metal is continually made up by the overflow whichhas been provided so that a re-pouring is not required and there is noentrainment of air.

With these and other objects in view which will become apparent in thefollowing detailed description, the present invention, which is shown byexample only, will be clearly understood, in connection with theaccompanying drawing, in which the only FIGURE is an axial section ofthe apparatus designed in accordance with the present invention.

Referring now to the drawing the apparatus, according to the presentinvention, comprises an ingot mold set defining a chamber 1, whichreceives molten metal from a connecting duct or an overflow 7. Thesurface of the molten metal 9 in chamber 1 is maintained on a constantlevel determined by level detector 8. The chamber 1 is provided at itslower end with a bottom opening 3 and is connected by said opening in anL- shaped arrangement to a bottom runner defining a second chamber 2. Atits end opposite to the bottom opening 3, the second chamber 2 has anoutlet opening 5 communicating with a removable mold 6. The distance Hfrom the bottom of the removable mold 6 to the bath level determined bylevel detector 8 is automatically held constant during the castingoperation by the provision of the overflow 7 according to the presentinvention.

A plug 4 is inserted into the bottom opening 3, and is connected to aguided stopper rod 11, which extends into the melt 9 freely from above.By means of a control lever 14, a mechanical control mechanism 13 andthe guided stopper rod 11, the plug 4 is raised or lowered as may berequired, thereby closing or opening the bottom opening 3. The guidedstopper rod 11 extends through the nips between two pairs of guiderollers 12 and above said rollers carries a weight 15. There is anadjustable vertical gap over the guided stopper rod 11.

When the molten metal flows from the melting chamber or ladle throughthe connecting pipe or overflow 7 into the chamber 1, the chamber willfill while the plug 4 is seated at the bottom opening 3. When the plug 4has been lifted from its seat, the chambers l and ,2 communicate and themolten metal in the chamber 2 is under the static pressure whichprevails at the bottom of the chamber 1 and depends on the head H andthe density of the molten metal. That pressure causes the molten metalto rise into the removable mold 10. through the outlet opening 5. In themold 10, the molten metal flows through runners to several mold cavitiesand through gates at the end of the runners into the mold cavities,which are filled by the molten metal in a bottom-pouring operation. Whenthe molten metal has entered the mold cavities, the bottom opening 3 ofthe chamber 1 can be closed by means of the plug 4, which is controlledby hand or automatically by a relay (not shown), which may be remotelycontrolled in response to a contact which is closed as the rising moltenmetal enters a sensing riser of the casting system.

The apparatus according to the present invention is generally used incasting operations and may be used for casting virtually any moltenmetal. The advantages of the apparatus according to the presentinvention will become particularly apparent where molten metals are usedwhich are easily oxidized.

The subject matter of the present invention is not restricted to theembodiment which has been shown and described by way of example tofacilitate the understanding of the invention, because said embodimentmay be modified within the scope of the present invention.

While I have disclosed one embodiment of the present invention, it is tobe understood that this embodiment is given by example only and not in alimiting sense.

lclaim: 1. An apparatus for casting molten metal, which comprises ahousing defining a vertically elongated first chamber, said firstchamber having a bottom formed with a bottom opening communicating withsaid first chamber, said housing being provided with inlet meanscommunicating with said first chamber on a predetermined intermediatelevel thereof and including means for automatically maintaining constantthe level of said molten metal in said first chamber during the castingoperation, said housing defining a horizontally elongated secondchamber, the latter being smaller in crosssectional area than said firstchamber and has one end portion communicating with said bottom openingand an opposite end portion formed with an upwardly directed exitopening, adapted to communicate with a bottom-pouring removable moldwhich is separate from said housing and disposed below said constantlevel of molten metal, a plug operable to selectively close and opensaid bottom opening, and means for heating the molten metal in saidfirst and second chambers. I 2. The apparatus, as set forth in claim 1,in which said inlet means comprises an overflow inlet.

3. The apparatus, as set forth in claim 2, in which said overflow inletcomprises an overflow inlet pipe connected to said housing. 4. Theapparatus, as set forth in claim 1, which comprises a bottom-pouringmold, which is mounted to communicate with said upwardly directed exitopening and has a mold cavity disposed below said intermediate level. 5.The apparatus, as set forth in claim 1, which comprises a stopper rodconnected to and extending upwardly from said plug in said first chamberand above said level of molten metal and guiding means disposed abovesaid level of molten metal and in guiding engagement with said stopperrod. 6. The apparatus, as set forth in claim 5, which comprises manuallyoperable means for operating said stopper rod to open and close saidbottom opening. 7. The apparatus, as set forth in claim 5, whichcomprises electrically controlled means for operating said stopper rodto open and close said bottom openmg. 8. The apparatus, as set forth inclaim 1, which comprises a source of molten metal in communication withsaid inlet means. 9. The apparatus, as set forth in claim 8, in whichsaid source comprises a melting furnace. 10. The apparatus, as set forthin claim 8, in which said source comprises a ladle.

1. An apparatus for casting molten metal, which comprises a housingdefining a vertically elongated first chamber, said first chamber havinga bottom formed with a bottom opening communicating with said firstchamber, said housing being provided with inlet means communicating withsaid first chamber on a predetermined intermediate level thereof andincluding means for automatically maintaining constant the level of saidmolten metal in said first chamber during the casting operation, saidhousing defining a horizontally elongated second chamber, the latterbeing smaller in cross-sectional area than said first chamber and hasone end portion communicating with said bottom opening and an oppositeend portion formed with an upwardly directed exit opening, adapted tocommunicate with a bottom-pouring removable mold which is separate fromsaid housing and disposed below said constant level of molten metal, aplug operable to selectively close and open said bottom opening, andmeans for heating the molten metal in said first and second chambers. 2.The apparatus, as set forth in claim 1, in which said inlet meanscomprises an overflow inlet.
 3. The apparatus, as set forth in claim 2,in which said overflow inlet comprises an overflow inlet pipe connectedto said housing.
 4. The apparatus, as set forth in claim 1, whichcomprises a bottom-pouring mold, which is mounted to communicate withsaid upwardly directed exit opening and has a mold cavity disposed belowsaid intermediate level.
 5. The apparatus, as set forth in claim 1,which comprises a stopper rod connected to and extending upwardly fromsaid plug in said first chamber and above said level of molten metal andguiding means disposed above said level of molten metal and in guidingengagement with said stopper rod.
 6. The apparatus, as set forth inclaim 5, which comprises manually operable means for operating saidstopper rod to open and close said bottom opening.
 7. The apparatus, asset forth in claim 5, which comprises electrically controlled means foroperating said stopper rod to open and close said bottom opening.
 8. Theapparatus, as set forth in claim 1, which comprises a source of moltenmetal in communication with said inlet means.
 9. The apparatus, as setforth in claim 8, in which said source comprises a melting furnace. 10.The apparatus, as set forth in claim 8, in which said source comprises aladle.